1. Field of the Invention
This invention pertains to wood burning stoves and furnaces, and more particularly to small, free-standing, high efficiency wood stoves designed to heat small areas for long periods.
2. Description of the Related Art
Wood burning stoves for structures with small living areas, such as boats, trailers or cabins must be compact and safe. Because of their small size, they can only burn small amounts of fuel at one time and must be highly efficient.
Large free-standing wood stoves use large primary combustion chambers that enable them to burn larger pieces of wood and produce more heat. The efficiency of a stove, regardless of its size, is determined by the combustion that occurs inside the stove and the heat transfer. While ideally the combustion and amount of heat transfer should be near 100%, no stove burns wood at these high efficiencies.
Complete combustion occurs inside a wood stove when an adequate amount of oxygen enters the stove so all of the carbon atoms and water molecules in the wood are converted to CO2 and released into the stove pipe. Heat transfer is 100% when all of the heat from combustion is transferred to the air and objects surrounding the stove.
In order for maximize combustion in a wood stove, an optimal volume of oxygen must be delivered to specific regions in the stove's combustion chamber. If too much oxygen is delivered or if it is delivered to the wrong region in the combustion chamber, combustion is incomplete. Ideally, a sufficient volume of oxygen should be delivered to the combustion chamber so it swirls forcibly around inside the combustion chamber and mixes with the combustion gases.
The heat transfer efficiency of a wood stove is dependent in part on the stove's structure, where high temperatures and greater turbulence of the gases occur inside the stove, and the exposure or residence time of the gases inside the stove and stove pipe. Higher temperatures, greater the turbulence, and slower movement of the gases through the stove, generate more heat transfer. Factors that control the velocity or movement of the gases through a stove include the design of the fire box and secondary structures inside the stove such as baffles, the size and shape of the stove pipe, and the height of the stove pipe that impede movement of the hot gases out of the stove.